DOI： 10.5194/acp-24-4851-2024

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DOI： 10.1186/s40623-024-01995-9

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DOI： 10.1038/s41598-022-11686-8

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DOI： 10.5194/amt-14-6509-2021

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DOI： 10.1017/exp.2021.6

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DOI： 10.5194/acp-21-2343-2021

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DOI： 10.1016/j.jastp.2020.105512

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DOI： 10.1016/j.jastp.2020.105339

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DOI： 10.1186/s40623-020-01229-8

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DOI： 10.1016/j.polar.2019.100501

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DOI： 10.1186/s40623-019-1093-8

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DOI： 10.1186/s40623-019-1070-2

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In order to understand the characteristics of long-lasting C-type structure in the sodium layer, six events were analyzed.

DOI： 10.1029/2019JA026630

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DOI： 10.1186/s40623-018-0864-y

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DOI： 10.1186/s40623-017-0677-4

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DOI： 10.1364/OE.25.00A491

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PubMed

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DOI： 10.1186/s40623-017-0643-1

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DOI： 10.1002/2016JA023472

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DOI： 10.1002/2016RS006035

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DOI： https://doi.org/10.1002/2015GL066411

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DOI： https://doi.org/10.5194/angeo-33-941-2015

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DOI： https://doi.org/10.1002/2015JA021000

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DOI： https://doi.org/10.1016/j.jastp.2014.11.006

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DOI： https://doi.org/10.5194/angeo-32-1195-2014

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DOI： doi:10.1029/2014JA020050

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DOI： https://doi.org/10.5194/angeo-32-831-2014

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DOI： https://doi.org/10.1002/2014GL060591

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DOI： 10.1002/2013JA019520

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DOI： https://doi.org/10.1002/2013JA018965

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DOI： https://doi.org/10.1002/grl.50897

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DOI： https://doi.org/10.1002/jgra.50414

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DOI： 10.1029/2012JA017928

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Data collected by the Stokkseyri SuperDARN HF
radar simultaneously at short and far ranges are used to investigate
the relationship between the velocity of E-region
HF echoes, E ×B electron drift and the isothermal ionacoustic
speed CS.

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2011GL048685

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We experimentally observe the location and angular size of the high-frequency (HF) radio window in the bottomside ionosphere, which permits radio wave propagation to the topside ionosphere, with high angular resolution at the European Incoherent Scatter (EISCAT) facility. HF pump-induced ion line enhancements were observed by the EISCAT UHF incoherent scatter radar on the ionospheric bottomside and topside.

DOI： 10.1029/2010JA016014

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DOI： 10.1029/2010JA016014

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DOI： 10.1029/2010JA015827

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To study the spatial structure of midlatitude sporadic E (Es) layers, the ultraviolet resonant scattering by magnesium ions (Mg+) in an Es layer was observed during the evening twilight with the Magnesium Ion Imager (MII) on the sounding rocket launched from the Uchinoura Space Center in Kagoshima, Japan. The in situ electron density measured by an onboard impedance probe showed that the Es layer was located at an altitude of 100 km during both the ascent and descent of the flight. Simultaneous observation with a ground-based ionosonde at Yamagawa identified the signature of horizontally “patchy" structures in the Es layer. The MII successfully scanned the horizontal Mg+ density perturbations in the Es layer and found that they had patchy and frontal structures. The horizontal scale and alignment of the observed frontal structure is generally consistent with a proposed theory. To our knowledge, this is the first observation of the two-dimensional horizontal structure of Mg+ in an Es layer.

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Ion outflow from the high‐latitude ionosphere is a well‐known phenomenon and an important source of plasma for the magnetosphere. It is also well known that pumping the ionosphere with high‐power high‐frequency radio waves causes electron heating. On a few occasions, this has been accompanied by artificially induced ion upwelling. We analyze such a controlled experiment at EISCAT up to 600 km altitude. The pump‐enhanced electron temperatures reached up to ∼4000 K above 350 km, and ion upwelling reached up to ∼300 m/s above 500 km altitude. The pump‐induced electron pressure gradient can explain the ion velocity below 450 km. Between 450 and 600 km the electron pressure gradient correlates equally with ion acceleration and ion velocity, which represents the transition altitude to free ion acceleration. The electron gas pressure gradient can explain ion upwelling, at least up to 600 km altitude. In addition, such active experiments open the possibility to estimating the F layer ion‐neutral collision frequency and neutral density with altitude from ground‐based observations.

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Simultaneous observations were conducted with 1 Introduction a Fabry-Perot Interferometer (FPI) at a wavelength of
557.7 nm, an all-sky camera at a wavelength of 557.7 nm, and the European Incoherent Scatter (EISCAT) UHF radar during the Dynamics and Energetics of the Lower Thermosphere in Aurora 2 (DELTA-2) campaign in January 2009. This paper concentrated on two events during periods of pulsating au- rora. The lower-thermospheric wind velocity measured with the FPI showed obvious fluctuations in both vertical and hor- izontal components. Of particular interest is that the location of the fluctuations was found in a darker area that appeared within the pulsating aurora. During the same time period, the EISCAT radar observed sporadic enhancements in the F-region backscatter echo power, which suggests the pres- ence of low-energy electron (1 keV or lower) precipitation coinciding with increase in amplitude of the electromagnetic wave (at the order of 10 Hz or higher). While we have not yet identified the dominant mechanism causing the fluctuations in FPI-derived wind velocity during the pulsating aurora, the frictional heating energy dissipated by the electric-field per- turbations may be responsible for the increase in ionospheric thermal energy thus modifying the local wind dynamics in the lower thermosphere.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Characteristics are presented of the lower thermospheric wind from a long run data set obtained by the EISCAT UHF radar at Tromsø (69.6°N, 19.2°E) over ~23 days, from September 6 to 29, 2005. The derived semidiurnal amplitude exhibited day-to-day variations (~5–30 ms-1) at and above 109 km, while the phase varied little with the day. We have found a mode change of the semidiurnal tide occurring during September 17–22, 2005. Between September 6 and 16, the vertical wavelengths were estimated to be ~58 km and ~76 km for the meridional and zonal components, respectively, while between September 23 and 29, they became less than ~24 km. The day to day variability of the diurnal tide was less obvious than that of the semidiurnal tide. The diurnal amplitude of the meridional component increased with height except for 8 days between September 13 and 20, when the diurnal amplitudes were smaller values (<40 ms-1) at and above 111 km than those for the other intervals. Furthermore, the shapes of the altitude profiles of the meridional phase differ from those for the other intervals. We have evaluated contributions due to the electric field and the ion drag acceleration and showed that they were not the causes. From the analysis of 22.5 days of wind data, we found about 5–6 day oscillations in the lower thermosphere, probably where there were planetary wave activities in the lower thermosphere.

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The influence of solar activity upon ion upflow in the polar ionosphere was investigated using data obtained by the European Incoherent Scatter (EISCAT) Tromsø UHF radar between 1984 and 2008. In agreement with other work we find that the upward ion flux is generally higher when solar activity is high than when it is low. Ion upflow events and also the upward velocity behave the opposite: they are more frequently seen and higher, respectively, at times of low solar activity. In any year about 30–40% ion upflow is accompanied by ~500 K higher electron temperature than the background temperature at 400 km altitude. Electron and ion heating in connection with upflow is nearly twice as prevalent during high solar activity as it is at low activity. The acceleration of ions by pressure gradients and ambipolar electric field becomes larger when solar activity is low than when it is high. This variation of the average acceleration is caused by the different shapes of electron density profiles for low and high solar activities. Ions start to flow up at above 450 km altitude when solar activity was high, and lower, at 300–500 km altitude, at low solar activity. It is suggested that the solar activity influences long-term variations of the ion upflow occurrence because it modulates the density of neutral particles, the formation of the F2 density peak, and ion-neutral collision frequencies in the thermosphere and ionosphere.

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We analyzed neutral winds, ambipolar diffusion coefficients, and neutral temperatures observed by the Nippon/Norway Tromsø Meteor Radar (NTMR) and ion temperatures observed by the European Incoherent Scatter (EISCAT) UHF radar at Tromsø (69.6°N, 19.2°E), during a major stratospheric sudden warming (SSW) that occurred in January 2009. The zonal winds at 80–100 km height reversed approximately 10 days earlier than the zonal wind reversal in the stratosphere and the neutral temperature at 90 km decreased simultaneously with the zonal wind reversal at the same altitude. We found different variations between geomagnetically quiet nighttime ion temperatures at 101–110 km and 120–142 km for about 10 days around the SSW. Our results from the ground-based observations agree well with the satellite observations shown in an accompanying paper. Thus, this study indicates that a SSW is strongly linked to thermal structure and dynamics in the high-latitude mesosphere, lower thermosphere, and ionosphere.

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A coordinated observation of the atmospheric response to auroral energy
input in the polar lower thermosphere was conducted during the Dynamics and
Energetics of the Lower Thermosphere in Aurora (DELTA)
campaign. N2 rotational temperature was measured with a rocket-borne
instrument launched from the Andoya Rocket Range, neutral winds were
measured from auroral emissions at 557.7 nm with a Fabry-Perot
Interferome-ter (FPI) at Skibotn and the KEOPS, and ionospheric parameters
were measured with the European Incoherent Scatter (EISCAT) UHF radar at
Tromso. Altitude profiles of the passive energy deposition rate and the
particle heating rate were estimated using data taken with the EISCAT radar.
The local temperature enhancement derived from the difference between the
observed N2 rotational temperature and the MSISE-90 model neutral
temperature were 70-140 K at 110-140 km altitude. The temperature increase
rate derived from the estimated heating rates, however, cannot account for
the temperature enhancement below 120 km, even considering the contribution
of the neutral density to the estimated heating rate. The observed upward
winds up to 40 m s¡1 seem to respond nearly instantaneously to changes in
the heating rates. Although the wind speeds cannot be explained by the
estimated heating rate and the thermal expansion hypothesis, the present
study suggests that the generation mechanism of the large vertical winds
must be responsible for the fast response of the vertical wind to the
heating event.

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We present quantitative radar observations of both hydrogen ion (H+) and oxygen ion (O+) upflow in the topside polar ionosphere using measurements that were recently carried out with the EISCAT Svalbard Radar and the Reimei satellite. H+ upflow was clearly observed equatorward of the cusp above 500 km altitude. Within the cusp the H+ density was very low, and the upflow was dominated by O+ ions, but on closed field lines the H+ became the larger contributor to the upward flux above about 550 km. The total flux seemed to be conserved, and so below 550 km altitude O+ (with a small upward velocity of ~50 m s–1) appeared to determine the upward flux which was then maintained by H+ in the topside ionosphere. We also found that the H+ density in the topside polar ionosphere was several times higher than current predictions of ionospheric models like IRI2001

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F region strong sunward ion flow embedded in the duskside cell of expanding polar cap ion convection and coincidental increase in the ion temperature were observed from about 73 degrees to 69 degrees in geomagnetic latitude between 16: 00 and 16: 48 MLT on 19 August, 2006 from an experiment using the European Incoherent Scatter (EISCAT) radars at Tromso, Sodankyla and Longyearbyen together with the CUTLASS HF radars. The spatiotemporal structure of the convection map obtained by the SuperDARN HF radars showed that the high-speed flow channel elongated in 14-17 MLT was moving equatorward. The flow channel appeared during an interval of negative interplanetary magnetic field B-z associated with large positive B-y. In order to evaluate ion frictional heating and resultant ion temperature increase quantitatively, the experiment was conducted to estimate the ion velocity vector and the ion temperature at the common scattering volume of the EISCAT radars. While the flow channel moved equatorward, the ion temperature increase became less evident at higher part of latitudes within the flow channel, which means that ion frictional heating was depressed where the neutral gases had already responded to the high-speed ions. The increase in the ion temperature at particular geomagnetic latitude continued for about 20 min, and then ceased while the ion velocity was still enhanced. Ion frictional heating lasted until the neutral wind was accelerated to the equivalent level of the surrounded ion flow.

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A case study with simultaneous European Incoherent Scatter and optical auroral observations was conducted in order to determine characteristics of the magnetosphere-ionosphere coupling from the viewpoint of the electrodynamics in the ionosphere. Particularly focused on were the relationships between ionospheric electron density depletion, perpendicular electric fields, and proton auroras. Intense electron density depletion was observed in the E and F regions poleward and in the vicinity of a thin equatorward moving arc. This depletion was associated with an intense, equatorward perpendicular electric field close to similar to 80 mV/m and most likely with a downward field-aligned current (FAC), but it did not accompany detectable proton aurora. Hence the downward FA electric field in the lower magnetosphere associated with this depletion was weak or absent. The motion of the FAC system with the depletion and the arc presumably enabled the downward FAC to obtain enough current carriers as ionospheric electrons were lost by the evacuation process. The evacuation process associated with the downward FAC was, however, efficient enough to establish the depletion. On the other hand, a widely distributed proton aurora observed immediately after the depletion was associated with an intense, equatorward perpendicular electric field close to 90 mV/m, enhanced electron density, and most likely a downward FAC. No electron precipitation was associated with this proton aurora. Thus the electron density enhancement, providing the downward current carriers, had to be caused by the ionization of precipitating protons presumably accelerated by downward field-aligned electric fields in the lower magnetosphere.

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Simultaneous observation with the Sondrestrom incoherent-scatter (IS) radar and the Reimei satellite was conducted on 3 October 2007. The objective was to measure horizontal patterns of the ionospheric structure in the vicinity of an auroral arc. The IS radar was scanned azimuthally with a fixed elevation angle, and the satellite narrow-view camera (557.7 nm) was directed downward taking pictures every 0.12 s. A stationary auroral arc was captured at 05: 17 UT (02: 54 MLT) with both instruments simultaneously. Gross ionospheric features measured with the IS radar around the arc were in good agreement with the expected magnetosphere-ionosphere current system. Of particular interest was the horizontal pattern in the ion speed and temperature in the F region. The ion speed within the arc was close to zero; by contrast the larger ion speed (350-400 m s(-1)) on the poleward side was parallel to the arc and almost no horizontal shear within about 20 km width perpendicular to the arc. This area was separated into two parts by the ion temperature: one was associated with clear enhancements in excess of 1200 K, and another was with more moderate enhancements (less than similar to 1000 K). The widths of the two areas were approximately 10 km each. The horizontal shear seen in the ion temperature suggested the presence of a narrow thermospheric wind shear of about 10 km width. This paper suggests that the possible cause for the thermospheric wind shear was ion drag associated with localized soft particle precipitation or F-region ionization.

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We have investigated how geomagnetic activity, the solar wind (SW), and the interplanetary magnetic field (IMF) influence the occurrence of the F-region/topside ionospheric ion upflow and downflow. Occurrence of dayside ion upflow observed with the European Incoherent Scatter Svalbard radar (ESR) at 75.2 degrees magnetic latitude is highly correlated with the SW density, as well as with the strength of the IMF By component. We suggest that this correlation exists because the region where ion upflow occurs is enlarged owing to SW density and IMF By magnitude, but it does not move significantly in geomagnetic latitude. The occurrence frequency of dayside ion upflow displays peaks versus the geomagnetic activity index (Kp), SW velocity, and negative IMF Bz component; that is, ion upflow is less frequently seen at the highest values of these parameters. Dayside ion downflow in the F-region/topside ionosphere occurs only when the Kp index and/or SW velocity are high or when IMF Bz is largely negative. The ion downflow is likely due to ballistic return of the ion upflow. We suggest that the region of ion upflow not only becomes larger but also moves equatorward with increasing Kp, SW velocity, and negative IMF Bz. The ESR can so be poleward of the upflow region and observe ions convecting poleward and returning ballistically downward.

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e analyzed data obtained with the European incoherent scatter (EISCAT) Svalbard Radar (ESR) at Longyearbyen (78.2 degrees N, 16.0 degrees E in geographic coordinates, 75.2 degrees Lambda in invariant latitude) to advance our understanding of the acceleration mechanism of the lower thermospheric neutral wind when the ionospheric convection becomes enhanced. The Advanced Composition Explorer satellite observed a southward turning in the interplanetary magnetic field at 0843 UT on 16 June 2005. At 0900 UT, the F region ion velocity and the lower thermospheric neutral wind ( at 118-km altitude) observed with the ESR began to accelerate significantly in the westward and northwestward directions, respectively. The neutral wind was remarkably accelerated within 1 hour from 0900 UT, and its speed became a value of similar to 500 m s(-1) at 1000 UT. The wind speed was significantly higher than a typical wind speed at 118 km. We evaluated the ion drag contribution on the generation of the high-speed neutral wind. Our evaluation verifies that the ion drag force could not generate the high- speed neutral wind within such a short time (similar to 1 hour). This result implies that the major driving force was the horizontal pressure gradient force induced by the Joule heating. We deduced the contribution of the pressure gradient force based on a quantitative estimation of the Joule-heating-induced pressure gradient from the ESR and the Super Dual Auroral Radar Network data. We concluded that the pressure gradient force was the most probable force in this event.

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Strong radar returns at VHF known as Polar Mesospheric Winter Echoes (PMWE) seem to occur during periods of intense ionisation of the mesosphere. Apart from a
mechanism to produce such ionisation, viz. solar proton precipitation, other prerequisites have been proposed, such as neutral air turbulence. Here, we employ a medium
frequency radar to examine whether the atmospheric state is conducive to the appearance
of PMWE; echo power signatures (isolated lower mesospheric echoes – “ILME")
are indicators of the necessary ionisation at sufficient depth in the middle atmosphere,
and also echo fading times give information on turbulence. We fail to find evidence for causal relationship between ILME and turbulence but suggest that on occasion turbulence
may be enhanced related to proton precipitation. The results presented provide
a basis for investigating whether turbulence is a prerequisite for PMWE.

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Using the European incoherent scatter (EISCAT) Svalbard radar located in Longyearbyen
(78.2° N, 16.0° E) and with the EISCAT UHF radar located in Troms? (69.6° N, 19.2° E),
we have analyzed the data obtained for six consecutive days from 1000 UT on 1 July 1999 to 1000 UT on 7 July 1999 to investigate the importance of ion drag on the lower thermospheric wind dynamics in the summer polar region. The electric field observed at Longyearbyen exhibited a stable diurnal variation primarily occurring throughout the first three days of observations, while during the latter three days the diurnal variation was not clearly identified. The electric field observed at Troms? did not exhibit such a stable variation. On the basis of the difference of the electric field variation observed at Longyearbyen, we divided the data sets into two intervals with a length of three days each. We compared the horizontal velocities of the ions and the neutral gases. At upper heights (～110-120 km) on the first three days, the difference between the ion and neutral motion was clearly identified at Longyearbyen, while it was not at Troms?. We compared the diurnal tidal amplitudes and phases of the two intervals derived from the Longyearbyen data. The amplitude of the meridional diurnal tide for the first three days was larger than that of the latter three days over the height region between 100 and 118 km at Longyearbyen. Furthermore, we compared ion drag accelerations with total accelerations. We concluded that the ion drag played an important role in the diurnal amplitude at Longyearbyen on the first three days of the observations. In addition, we compared the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics general circulation model (TIME-GCM) predictions with the observations. The TIME-GCM predictions also indicated that the diurnal tide is influenced by the convection electric field.

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From simultaneous observations of the European incoherent scatter Svalbard radar (ESR) and the Cooperative U.K. Twin Located Auroral Sounding System (CUTLASS) Finland radar on March 9, 1999, we have derived the height distributions of the thermospheric heating rate at the F region height in association with electromagnetic energy inputs into the dayside polar cap/cusp region. The ESR and CUTLASS radar observations provide the ionospheric parameters with fine time-resolutions of a few minutes. Although the geomagnetic activity was rather moderate (Kp = 3+ ~ 4), the electric field obtained from the ESR data sometimes shows values exceeding 40 mV/m. The estimated passive energy deposition rates are also larger than 150 W/kg in the upper thermosphere over the ESR site during the period of the enhanced electric field. In addition, enhancements of the Pedersen conductivity also contribute to heating the upper thermosphere, while there is only a small contribution for thermospheric heating from the direct particle heating due to soft particle precipitation in the dayside polar cap/cusp region. In the same period, the CUTLASS observations of the ion drift show the signature of poleward moving pulsed ionospheric flows with a recurrence rate of about 10–20 minutes. The estimated electromagnetic energy deposition rate shows the existence of the strong heat source in the dayside polar cap/cusp region of the upper thermosphere in association with the dayside magnetospheric phenomena of reconnections and flux transfer events.

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We have examined the temporal development of an established proxy for turbulent intensity for the mesosphere/lower thermosphere region above Tromsoe (70°N, 19°E) for the period 1999 to present. We find an indication of steadily increasing turbulence in the mid-mesosphere, the height of the demarcation between positive and negative trends varying somewhat with season. Although beyond the scope of this study, anthropological sources, causing lower atmosphere warming and upper atmosphere cooling, are strong candidates for the underlying cause of the trend.

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This paper aims at describing the ionospheric conditions during the DELTA campaign period based on EISCAT radar observations conducted at Tromsoe (69.6°N, 19.2°E). Observed electron densities and derived electric fields by the EISCAT UHF radar indicate that magnetospheric activity was high during the period from December 5 to 13 except for the night of December 13. Derived semidiurnal amplitudes during December 9-12, 2004 exhibited a day to day variation at and below 110 km. Neutral and electron temperatures measured by the DELTA rocket were compared with neutral/ion and electron temperatures from the EISCAT UHF radar observations. Comparison of neutral/ion temperatures show some agreement, while poor agreements were found for the electron temperature. Possible causes of the discrepancy are discussed.

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Simultaneous Incoherent Scatter radar observations using two EISCAT radars, the Troms? (69.6°N, 19.2°E) UHF radar and the EISCAT Svalbard radar (Longyearbyen 78.2°N, 16.0°E) were conducted for eight consecutive days, from November 11 to 19, 2003, to study the lower thermospheric wind dynamics in the polar region. This kind of long-run data sets was rare, and this was the first 8-day long run made in winter by the EISCAT Troms? radar. Derived wind data were analyzed, in particular, in terms of the latitudinal difference of the mean wind and diurnal and semidiurnal tides as well as the presence of the quasi-two day wave (Q2DW) in the lower thermosphere.

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Event date： 2024.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：国立極地研究所   Country：Japan  

Event date： 2024.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学   Country：Japan  

Event date： 2024.1 - 2024.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Bern   Country：Switzerland  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東北大学   Country：Japan  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2023.4

Language：Japanese  

Venue：名古屋大学   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ZOOM   Country：Japan  

Event date： 2023.3

Language：Japanese  

Venue：ZOOM   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ZOOM   Country：Japan  

Event date： 2023.3

Language：English   Presentation type：Poster presentation  

Venue：Tachikawa, Tokyo   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：相模原市立産業会館   Country：Japan  

Event date： 2022.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Sundbyholm Castle and ZOOM   Country：Sweden  

Event date： 2022.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari, Chiba   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.2

Language：English   Presentation type：Oral presentation (general)  

Venue：on-line   Country：India  

Event date： 2021.11

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.11

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.5 - 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：on-line   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ZOOM  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ZOOM  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ZOOM  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ZOOM  

Event date： 2020.12

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.11

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.7

Language：English   Presentation type：Poster presentation  

Venue：JpGU  

We have reported statistical studies of sporadic sodium layer observed with the Sodium Lidar at Tromsoe.

Event date： 2019.12

Language：English   Presentation type：Poster presentation  

Venue：Tachikawa, Tokyo   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2019.3

Language：English   Presentation type：Oral presentation (general)  

Venue：UiT The Arctic University of Norway, Tromsoe   Country：Norway  

Event date： 2019.3

Language：English   Presentation type：Oral presentation (general)  

Venue：UiT The Arctic University of Norway, Tromsoe   Country：Norway  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：立川、東京   Country：Japan  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：立川、東京   Country：Japan  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：立川、東京   Country：Japan  

Event date： 2018.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Tachikawa, Tokyo   Country：Japan  

Event date： 2018.11

Language：Japanese   Presentation type：Poster presentation  

Country：Japan  

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Poster presentation  

Venue：小金井   Country：Japan  

Event date： 2018.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2018.5

Language：Japanese  

Venue：立川、東京   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：立川、東京   Country：Japan  

Event date： 2018.4

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：立川、東京   Country：Japan  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：立川、東京   Country：Japan  

Event date： 2017.12

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.11

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.9

Language：English   Presentation type：Oral presentation (general)  

Venue：UiT The Arctic University of Norway, Tromsoe   Country：Norway  

Event date： 2017.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Tachikawa, Tokyo   Country：Japan  

Event date： 2017.5

Language：English   Presentation type：Poster presentation  

Venue：Makuhari, Chiba   Country：Japan  

Event date： 2010.12

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Country：Japan  

Event date： 2010.12

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2010.12

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2010.11

Language：English   Presentation type：Oral presentation (general)  

Event date： 2010.11

Language：English   Presentation type：Oral presentation (general)  

Event date： 2010.10

Language：English   Presentation type：Oral presentation (invited, special)  

Country：Japan  

Event date： 2010.6

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Country：Japan  

Event date： 2010.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2010.2

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2009.11

Language：Japanese   Presentation type：Poster presentation  

Country：Japan  

Event date： 2009.11

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2009.10

Language：English   Presentation type：Oral presentation (general)  

Event date： 2009.9

Language：Japanese   Presentation type：Poster presentation  

Country：Japan  

Event date： 2009.8

Language：English   Presentation type：Oral presentation (general)  

Event date： 2009.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2009.3

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2008.11

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2008.10

Language：English   Presentation type：Oral presentation (general)  

Event date： 2008.10

Language：English   Presentation type：Oral presentation (general)  

Event date： 2008.10

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2008.8

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2008.8

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

野澤悟徳、大山伸一郎、藤井良一、小川泰信

Event date： 2008.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2008.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2008.3

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

我々のグループが進めている、北欧拠点計画を紹介し、共同研究について議論した。

超高層大気物理学に関する専門書を輪読する。学生は、担当した箇所を予習し、発表スライドにまとめ、セミナーにて発表する。それを踏まえ、参加者全員で、議論を行う。

A student on duty read an assigned part of an English textbook in advance, understand it, and present it at class. All the students attending the class are recommended to join discussion about topics presented by the speaker.

超高層大気について、講義する。

太陽地球系科学について、オムニバスにて講義する。